A kinetic study of inosine nucleosidase from Azotobacter vinelandii |
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| Affiliation: | 1. Department of Biochemistry, Yokohama City University School of Medicine, Fukuura 3-9, Kanazawa-ku, Yokohama 236 Japan;2. Research Laboratory, Tokyo Zouki Chemical Company, Togane, Chiba 283, Japan;3. From the State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China and;4. the Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai 200237, China;1. Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, mizu, Toyama 939-0398, Japan;2. Toyama Institute of Health, 17-1 Nakataikoyama, Imizu, Toyama 939-0363, Japan;1. Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan;2. Department of Pharmaceutical Sciences, Tohoku University Hospital, Sendai 980-8574, Japan;3. Department of Biophysical Chemistry, Faculty of Pharmacy, Meijo University, Nagoya 468-8503, Japan;4. Tohoku Medical Megabank Organization, Tohoku University, Sendai 980-8575, Japan |
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| Abstract: | - 1.1. Inhibition of inosine nucleosidase from Azotobacter vinelandii by ATP and bases can be qualitatively and quantitatively accounted for by the partial noncompetitive inhibition mechanism with ligand exclusion model.
- 2.2. The enzyme has two binding sites for the substrate with equal affinity in the absence of the inhibitor. and two species of the inhibitor sites: I1- and I2-sites. The I1-site may overlap part of each substrate binding sites, and the I2-site is separated from the substrate sites.
- 3.3. ATP binds to the I1-site of the enzyme, and prevents the substrate from binding to either of two identical sites, producing the cooperativity with inosine, whereas binding of ATP to the I2-site causes a noncompetitive inhibition.
- 4.4. Adenine and hypoxanthine bind to the I2-site of the enzyme, and the EIS complex is partially active, resulting in a partial noncompetitive inhibition with Michaelis-Menten kinetics.
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